How much water ? several ways - insulated tank and take the hot water from home, chlorifier tank and use the engine to warm the water on route or install a gas water heater which much has been talked about on the window forum. Can you not just use the water heater on the carpet machine ? pre spray with the wand therefore hot pre spray, agitate, extract again hot. If you hav'nt got a built in heater get an in line heater, thats what I have